VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1938 Master Coupe "shudders"

When I first got my 38 coupe back on the road after restoration a couple years ago, it had a shimmy at the front wheels at about 30-40 mph. I had my tires rebalanced and the shimmy disappeared. But then I noticed that when I get up to about 45-50 mph., there is something that I can describe only as a kind of "shudder", not in the front, but seemingly in the middle or rear portion of the car. As soon as I back off the speed and bring it down to 35-40 mph., the "shudder" disappears and the car drives like a dream. I balanced and re-balanced the rear tires, rotated them, and that has had no effect. Could this be a bad U-joint? Or might I need to install a new Oakie bushing? Or am I entirely off track? If so, what might be causing this shudder?

Any thoughts will be greatly appreciated. Thanks in advance.

Yours,

Jim

If a rim is bent, rebalancing won't fix it. I had it happen on a newer car once. Only noticed it at 40mph+...

I recently had an experience similar, very similar, to what you are writing about. I explained it to a friend who worked in a brake shop for years. He told me that if the brakes are adjusted to tight on a vehicle or it maybe the brake pedal is not totally releasing, or the emergency brake is partially on, this is what can happen. I can't tell you anymore, but you might check your brakes.

Your problem could be the U-Joint or a bent drive shaft.

Ray, what can cause a bent driveshaft? Common? Thanks

I run into a rear end that had obviously been in a wreck. To connect the torque tube I had to use a come-a-long to move it almost 6 inches out of line to make the U-Joint connection. I could easily feel the complaint from the drive line.

It is possible that the torque tube was bent and not the shaft. I did not disassemble it to find out.

'Might be a U-joint and/or a torque tube bushing (?).

Thanks for your ideas. I rotated the tires from front to back at one point, so I'm doubtful that it's a tire or bent rim.

Is there an easy/sure-fired way to check the quality of the U-joint while still on the car? Or the bushing?

Joe, the brake idea is one that I didn't think about, seeing that it only happens at fairly high speeds; but it's worth a check.

I suppose this might be one of those diagnoses that one takes step by step, eliminating possibilities as you go along.

Any further wisdom is welcome.

Thanks,

Jim

Jim

I think you have a bent rear wheel or a unbalanced tire ("Casing" to Tiny and Uncle Ed). As others have pointed out, it could be several things. Something harmonically induced. Good luck with finding the offending part(s).

Not to fret, though. There is a simple solution to the phenomena: Avoid speeds of 45-50 MPH. Just drive at speeds that promote that "drives like a dream" feeling.

Or, get yourself a 235 or 261 and install it. That way the time lapse going through that creepy speed range will be short lived and you'll hardly notice the annoying "shudder" as you described it.

Actually, shudder is what a 1941 does whenever a 1938 comes near it. Sort of like how a thoroughbred does when it wants to avoid a pesky horsefly. I think you meant vibration. Just sayin'.

Charlie

I'm betting on the bushing.

When I was about 13, we had a '42 MD TS that developed a shudder-type vibration about 45-50 mph. It was the torque tube bushing. (Funny how things stick in one's mind.)

Good luck with your problem.

(Ain't these ol' Cars fun!)

I would say the U joint or the drive shaft bushings. If it is the U joint it can do more damage so I wouldn't drive it too much.